Widespread Indo-West Pacific, but west Indian Ocean population considerably different. Coastal to outer reef flats subject to currents and surge, often very shallow and usually in depths of less than 10m. Juveniles secretive in Acropora thickets, swiming just above to feed on plankton. Large adults swim about openly and graze algae, sometimes forming schools to feed on plankton. Length reported to 26cm, but usually to 20cm in the West Pacific.